Add tests for user_group_distinguished_names()

In https://github.com/stackabletech/opa-operator/pull/622#top we added an Active Directory backend to the user info fetcher.

As part of this, there was fairly extensive code to convert between some weird representations which AD chose for userids and groupids.

In order to not block the release with this we decided to punt on adding unit tests (hopefully, worst case: integration tests) for this later.

We should try and get this done fairly soon after 24.11.

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• Describe the use-case, as far is possible. For instance, using the pattern "As a XXXX, I would like XXXX to be able to do XXXX" helps to identify the feature as well as the problem it is intended to address.
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• Indicate if there is a known work-around until such time as the issue has been implemented.

Beginnen Sie mit dem in pull request 622 hinzugefügten Implementierungs- und Konvertierungscode, insbesondere mit dem Pfad user_group_distinguished_names(). Fügen Sie Unit-Tests oder, falls erforderlich, Integrationstests hinzu, die die Darstellungen der Benutzer- und Gruppen-IDs in Active Directory abdecken; abgeschlossen ist die Aufgabe, wenn das Konvertierungsverhalten getestet wird, ohne den Release zu blockieren.